1. Field of the Invention
The present invention relates to a device for spreading paste on paperboard in a corrugated board manufacturing apparatus and, more particularly, to a device for spreading paste on tops of core paper corrugatedly supplied from a pair of stepped heating rollers to be pasted with linerboard.
2. Description of the Prior Art
In a conventional corrugated board manufacturing apparatus, pasting for core paper is conducted by a roll turning system in which liquid paste having low viscosity is dipped up by a paste spreading roller to be spread on top of the corrugated core paper, which is then pasted with linerboard. Therefore, it has been desired that the liquid paste spread on the tops of the corrugation is impasted to gel and have high viscosity by heat from the stepped heating rollers while the core paper is moved toward the linerboard.
However, in a conventional device, a predetermined volume of the liquid paste is constantly stored in a tank placed in the vicinity of the stepped rollers and, therefore, the liquid paste is exposed to heat radiation from the stepped rollers, leading to gelation and deterioration of the paste which cannot be satisfactorily dipped up by the paste spreading roller.
Further, the effective width of the paste spreading roller is in conformity with the maximum width in varieties of sizes of the core paper and, thus, in case the outer periphery of the paste spreading roller is continuously in contact with the liquid paste stored in the tank, the roller dips up the liquid paste in a full width thereof during rotation. Because of this, when core paper, which is smaller in width than the paste spreading roller is used, excessive paste runs over both sides of the core paper leading to inferior pasting of the core paper, spreading of the paste to the outer peripheries of the stepped rollers and a press roller, sticking of the core paper and the linerboard to the rollers and exfoliation and breakage of the core paper and the linerboard.
In consideration of these disadvantages, there has been provided a device in which a pair of partitions are movably placed in the paste tank to adjust the width of the paste spreading roller which is in contact with the liquid paste stored in the tank in conformity with the width of the core paper to be pasted (Japanese utility model publication No. 41-21028).
In this device, however, the liquid paste stored between the partitions is still exposed to heat radiation from the stepped rollers, resulting in deterioration of the paste and, further, tends to run over the partitions to be spread on the outer peripheries of the rollers, resulting in exfoliation and breakage of the core paper and the linerboard.